1. Field of the Invention
Example embodiments relate to a semiconductor device and a method of using the same. Other example embodiments relate to a polymer, a top coating layer, a top coating composition and an immersion lithography process using the same.
2. Background of the Invention
As semiconductor devices become more integrated, finer and more exact patterning may be necessary. The critical dimensions of photoresist patterns formed during an exposure process are determined by Rayleigh's equation R=(k1)(λ/NA) wherein R represents resolution, k1 represents a process constant, λ represents a wavelength of a light source and NA (Numerical Aperture) represents an effective diameter of a lens. In order to reduce the resolution, the process constant (k1) may be smaller, the wavelength of a light source (λ) may be shorter and/or the effective aperture of a lens (NA) may be increased.
In order to generate a light source having a lower wavelength (λ) than KrF (248-nm) or ArF (193-nm), an exposure process may be performed using EUV (Extreme Ultraviolet) as a light source having a wavelength (λ) of 13.4 nm. The exposure process using EUV may necessitate different (or alternative) conditions than conventional exposure processes. Exposure equipment used for EUV may be costly. Due to the difficulties associated with using EUV, it may be desirous to perform the exposure process using an alternative light source and/or method.
In Rayleigh's equation, NA may be proportional to n(sin θ) wherein n represents a refractive index of a medium between a lens and a photoresist. If n increases, then the resolution (R) decreases.
In an exposure process exploiting the relationship between the resolution and the refractive index, an immersion lithography process may be performed. The immersion lithography process may be performed using ArF as a light source in a medium having a higher refractive index than air. Water has a refractive index of 1.44, and air has a refractive index of 1. As such, water may be used as the medium.
If the immersion lithography process is performed using water as the medium, then a photosensitive polymer, a photo-acid generator and a solvent in a photoresist layer contacting water may dissolve in water. If the immersion lithography process is performed using the water as the medium, air bubbles may form at an interface between water and the photoresist layer, making formation of exact photoresist patterns more difficult.
Because of the solubility of the polymer, the generator and the solvent in water and/or the formation of the bubbles, a top coating layer may be necessary. The top coating layer may protect the photoresist layer from water. The top coating layer may have a stronger hydrophobicity, and thereby insoluble with the photoresist layer. The top coating layer may have a light transmitting property. The top coating layer may be more easily removed with a developer.